The present invention generally relates to heart valve repair and replacement techniques and apparatus. More specifically, the invention relates to the repair of heart valves having various malformations and dysfunctions.
The mitral valve depends on adequate apposition or alignment between the anterior and posterior leaflets along a relatively long surface area under high pressure conditions. Typically, the contact surface is about 12 mm in a direction perpendicular to the anterior-posterior direction and this provides little margin of safety. The leaflet margins are attached to numerous fine chords suspended from attachment points along the inner surface of the left ventricle. Although these attachments are often referred to as papillary muscles, there is often a very diffuse arc-shaped attachment for each of the groups of chords to the endocardial surface. Unfortunately, this anchor point (i.e., the inner wall of the left ventricle) must move with each heartbeat and so the distance between the attachment of the leaflet edges is constantly changing. The chordal lengths may also changexe2x80x94typically increasing with age and degeneration and the chords frequently do not lengthen in a symmetrical fashion. This leads to variations in their lengths at all-important points of coaptation. Chords may also rupture. In addition, the mitral annulus changes diameter with each heartbeat such that it surface area changes by about 40% with each systole. As the heart enlarges, the annulus of the mitral valve can enlarge as well. In short, there are many variables affecting proper functioning of the mitral valve. The anatomy, such as the leaflet length, the chordal length and the annular length/diameter can change. The attachment points can change as the ventricle changes shape. More importantly, all of these aspects can change simultaneously. For example, a patient may have ischemic mitral regurgitation which pulls the posterolateral valve attachments away from their natural coaptation points and leads to an opening in this area of the mitral valve. This can be further affected if the chordal lengths are changed by even minor degrees of degenerative disease.
Mitral valve pathology has changed remarkably since the origin of open heart surgery one generation ago. Initially, the most common pathology or condition was rheumatic mitral valve disease. This produced thickened, impliable leaflets with grossly deformed chords, or chordae tendinae, often combined with fusion of the two leaflets. This valve was not suitable for any type of plastic procedure and, accordingly, numerous valve prostheses were developed to replace the entire valve, i.e., the annulus, leaflets and chords. Now, except in centers with high rates of immigration from third world countries, rheumatic mitral valve disease is a relatively uncommon indication for surgery. Various forms of degeneration ranging from gross billowing of leaflets to relatively minor chordal lengthening as well as ischemic mitral valve pathology are most commonly encountered. Recently, it has become apparent that combinations of these two problems are relatively common. In both of these situations, the mitral valve leaflets are soft, pliable and can be retained over the long-term in various repair procedures. Unfortunately, despite the fact that the leaflet tissue is suitable for retention, mitral repair is performed for less than half of the cases where mitral regurgitation is the problem. In surgical centers where mitral repair is not practiced, valves are often discarded and replaced.
One main problem is that mitral valve repair technology has not kept pace with the change in mitral valve pathology. Mitral valve repair is more an art than a science and requires a constant interaction between visual inspection and post operative results, as evidenced by transesophageal echocardiography (TEE). Few surgeons or surgical centers are equipped for or capable of performing this type of work on a routine basis. Many surgeons only perform mitral annuloplasty with rings that reduce the diameter of the annulus. These rings may appear to be a solution for a variety of problems but are not ideal for many ischemic and degenerative disease conditions.
Despite many attempts, the homograft mitral valve replacement is not an operation which can be performed reliably. It could have potential advantages in third world countries or in cases of infection. Failures occur because of the unreliability of attachment of the chords to the left ventricle. It is not difficult to anchor the valve in the annulus. However, it is virtually impossible to ensure that the chords are correctly spaced inside the ventricle to produce a competent valve. Again, the inner surface of the ventricle is a moving surface and it is almost impossible to guarantee that a chord extending from a leaflet edge will be fixed in such a way that the anterior and posterior leaflets are reliably aligned during valve operation.
Various other repair procedures are performed, but these are limited to the removal of leaflet tissue which is poorly supported and to chordal shortening and replacement. Many valves simply remain unrepaired due to the shortage of acceptable techniques and apparatus. The sophisticated procedures are acquired art forms that many surgeons either cannot master or do not have the time and opportunity to master.
Thirty years of valve surgery have indicated that the native leaflet tissue is the most reliable valve material. Despite numerous attempts to produce durable leaflet replacements, none have been found. The cost of demonstrating the value of a new material is extremely high. However, chordal replacement with polytetrofluorethylene is durable and highly satisfactory. Therefore, this at least provides a proven, reliable material to suspend leaflet tissue.
It is also clear that annuloplasty rings are durable, well-tolerated and do not require long-term anticoagulation. They fix the annular dimensions and reliably reduce one of the most important variables (i.e., the mitral annulus diameter) in mitral valve competence.
Regulatory issues in this field are the single most expensive factor. Next generation valve prosthesis designs are therefore most desirably based on the numerous available annuloplasty devices.
To properly and consistently repair the mitral valve, these variables must be fixedxe2x80x94the annular diameter, the leaflet length, the chordal length and the attachment point of the chords. Fortunately, the leaflet length is relatively constant. The annulus diameter can be fixed by the annuloplasty ring. The chords can be replaced by polytetrofluorethylene suture to fix their length. The missing variable is the attachment of the chords to the left ventricle. To date, this remains a troublesome variable to the valve repair.
Ischemic mitral regurgitation occurs when there is ventricular dysfunction which causes the posterolateral attachments of the mitral valve to be drawn away from the annulus in systole. This pulls the two leaflet edges apart at their point of coaptation and produces an asymmetrical regurgitant jet or, in other words, blood flow in the wrong direction through the valve. In its pure form, the leaflets, the chords and the attachment points are all anatomically normal. Sometimes there is a relative discrepancy between the distance the anterior leaflet is drawn inward relative to the posterior leaflet so they are not just separated from edge-to-edge but also there is a step deformity of the junction point. The patient may also have some underlying mild degree of degenerative deformity which may initially cause a mild, but well-tolerated degree of mitral regurgitation. However, the regurgitation often becomes severe after left ventricular ischemia occurs.
Some repair techniques apply tight annuloplasty rings which serve to buckle the leaflets and draw them together. This often leaves a degree of mitral regurgitation and mitral stenosis results. Annuloplasty can be accompanied by a modification of the Alfieri edge-to-edge repair, more recently referred to as the bowtie repair. With this technique, the surgeon merely sews the anterior leaflet to the posterior leaflet at the point of maximal distraction. This produces a two orifice valve with more stenosis.
Devices and methods are necessary that preserve the leaflet tissue but provides for virtually guaranteed coaptation of the leaflets by fixing some of the variables responsible for regurgitation. Other devices and methods are necessary that do not simply reduce the diameter of a heart valve annulus, but allow more specialized treatment tailored to patient needs.
Degenerative disease generally involves a relatively normal leaflet which is poorly supported by lengthened or ruptured chords. By attaching the poorly supported leaflet to replacement or native chords connected with a post in the left ventricle, a guaranteed point of coaptation can be produced. In this regard, one general form of the invention provides a device for supporting a heart valve in a patient with the heart valve including an annulus generally lying in a plane and a plurality of leaflets connected therewith and adapted to open and close to selectively allow and prevent blood flow. The device comprises a support member configured for attachment to the heart valve and the above-mentioned post extending from the support member and configured to extend away from the plane of the annulus. A connector is coupled with the post and configured for attachment to at least one of the leaflets. The post can support the posterior leaflet (extending from the posterior part of the support member), the anterior leaflet (extending from the anterior part of the support member) or both leaflets. For example, this would require a relatively simple modification of the currently available annuloplasty rings or other support members, for example, which may be ring segments. The connector may be one or more flexible tensile members, such as replacement chords passing from the leaflet(s), through or along the post and up to the support member. These flexible tensile members may be precisely length adjusted to bring the unsupported leaflet edge to the precise depth. This could replace the current posterior leaflet resection. It would also be a solution for the anterior leaflet repair which has produced only marginal results in most hands. The invention is also applicable to replacement heart valves formed of biologic or artificial materials. Various aspects of the invention are applicable to the repair of native valves, while other aspects apply to replacement valves of artificial biocompatible material, animal valve tissue or human valve tissue.
A device constructed in accordance with the invention would preferably fix the annular diameter, the chordal length and the point of chordal fixation in the ventricle. In this way, the invention provides a more reliable and permanent solution to the problems associated with the valve repair. Furthermore, it would be easy to perform by most surgeons. A small incision could be made in the annular attachment of the poorly supported anterior leaflet and the post passed through this incision. The support member would then be attached to the native annulus. Flexible tensile members, such as artificial or natural chords would then be attached from the post to the unsupported edge of the leaflet and adjusted by pulling them to length and fixing them. In the case of replacement chords, they are preferably fixed at the level of the support member. Devices could include posterior posts, anterior posts or both. A variety of possibilities exist for modified structures, including multi-forked posts or surgeon-created posts. It would also be preferable to provide chordal patterns to attach the posts to the leaflets and to develop a quick connect system for attachment of the chords to the leaflet edges. Adjustability of the system will be important in many cases for fine tuning.
Another form of the invention comprises a support member, which may be an annuloplasty ring or other support structure, and at least one post. A first chord gripping member is coupled with the post and configured to grip at least one of the chords and thereby fix the length of the chord between the first gripping member and the leaflets to support and align the leaflets for coaptation during operation of the valve. In the case of mitral valve repair, the post extends into the left ventricle taking origin from the posterolateral commisure. In a preferred embodiment, one gripping member traps the chords to the anterior leaflet in such a way that their distance from the leaflet edge is precisely fixed. A second post and gripping member can do the same for the posterior leaflet. The surgeon would then confirm that the gripping members had captured the chords precisely so that the leaflets meet exactly in systole. If there would be any doubt about this coaptation or should there be a fear of late failure due to chordal rupture, the native chords could be augmented or replaced by an array of replacement chords suspended from the posts and attaching to the leaflet edge. One may also postulate improved left ventricular function from the device since the bulging of the posterior wall of the heart will be prevented by the tethering of the chords which are trapped in the device.
The various devices of this invention are formed of biocompatible materials including, but not limited to, exposed biocompatible metals, fabric covered metal or polymer, exposed polymer, or any other biocompatible artificial or biologic material. The various devices of this invention may also be incorporated into a full replacement heart valve structure again formed from any biocompatible material for cases necessitating full replacement of the valve. In these cases, the replacement valve is fully supported in a position ensuring accurate coaptation of the valve leaflets and less stressful interaction of the valve leaflets with each other as well as with the valve commisures.
Another aspect of the invention provides a device for supporting a heart valve in a patient comprising a support structure configured for attachment to the heart valve annulus and a post connected to opposite sides of the support structure and configured to extend from one side of the annulus to another side thereof. This modifies the shape of the annulus, for example, to correct for ischemic condition. The post may be contained substantially in the same plane as the support structure and valve annulus or may extend substantially out of the plane containing the support structure and valve annulus. If extending substantially in the same plane, the post prevents outward bellowing of the valve leaflets, while if extending substantially out of the plane, the post simply functions to connect and modify the shape of opposite sides of the annulus. The post may be length adjustable to allow variable modification of the annulus and may include additional posts of adjustable length or fixed length. As with other embodiments of the invention, the support structure may comprise a ring-shaped member or one or more discrete support segments.
As another manner of correcting an ischemic condition, for example, a ring-shaped support member is provided having an asymmetric-shape about two perpendicular axes. Stated more generally, one side of the ring-shaped support member may be of narrower width than an opposite side of the ring-shaped support member. This may or may not be coupled with a slight angling downward of one side of the ring-shaped support member with respect to the opposite side of the ring-shaped support member. These modifications help to close a gap created between the valve leaflets due to conditions such as an ischemic condition.
In another aspect of the invention, a device is provided for adjusting the distance between a papillary muscle and an annulus of a heart valve. This device comprises a support member configured to be affixed to the annulus of the heart valve and an elongate flexible tensile member having first and second ends with the first end adapted to be fixed to the papillary muscle. A connector is configured to connect with the elongate flexible member and with the support member in a manner allowing adjustment in the length between the papillary muscle and the support member and fixation of the elongate flexible member at a desired length between the papillary muscle and the support member. Generally, this device is useful for setting the critical distance between the papillary muscle and the valve annulus and may be used in preparation for the various valve replacement and repair techniques and devices disclosed herein.
In another aspect of the invention, a device is provided for supporting a heart valve in a patient and generally comprising a support member adapted to be affixed to the annulus and having at least one selectively adjustable portion allowing one section of the support member to be moved with respect to another section thereof and locked in place in order to maintain one or both of the annulus and the leaflets in a desired configuration. The support member may be ring-shaped, for example, and may be selectively adjustable such that one section, lying in a single plane, may be adjusted and angled away from a plane containing another section of the ring-shaped support member. Alternatively, or in addition, the ring-shaped support member may be adjustable to allow one section to be narrowed in width with respect to another section. This feature is also advantageous for correcting ischemic conditions.
In one general method of supporting a heart valve in accordance with the invention, a support structure is first connected to the heart valve annulus. A post is then fixed to the support structure, or the support structure may already have a post extending therefrom. The post is then connected to one of the valve leaflets to support the leaflets during opening and closing thereof. In accordance with the various aspects of this invention, the post may be connected to the leaflet with a flexible tensile member, such as a natural or artificial chord, or may be more directly connected to the leaflet. One direct connection includes extending a wire coil from the post into two adjacent leaflets to connect central portions of leaflets together. Other possible connections include the artificial or natural chord connections mentioned above.
Various objectives, features and advantages of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description taken in conjunction with the the accompanying drawings.